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Abstract:
We discuss the temperature (T) dependence of the generalized density of
states G(omega, T) and of the phonon intensities of the filled
skutterudite compound YbFe4Sb12 investigated by inelastic neutron
scattering in an extensive range of energy-momentum phase space. The
inelastic response has been measured at T = 1.7, 50, 100, 200, and 290 K
at a thermal time-of-flight spectrometer with an incident wavelength of
1.3 angstrom. The experimentally determined signal is compared with
T-dependent ab initio powder averaged lattice dynamics calculations. An
additional set of T-dependent spectra is calculated with thermal
displacement parameters extracted from neutron diffraction data within
the incoherent approximation. G(omega, T) shows a nonuniform intensity
variation with T due to the specific thermal displacement parameters of
Yb, Fe, and Sb. We demonstrate that this temperature variation can be
well reproduced by the two simulation approaches. In particular, the ab
initio powder averaged lattice dynamics calculation is capable of
reproducing the momentum and energy characteristics of the phonon form
factors of YbFe4Sb12.
